The present invention relates to analog to digital converters (ADC) and more particularly to ADC's for converting charge-based signals.
Conventional ADC's operate by comparing a sampled analog voltage to a reference voltage, and adjusting the reference voltage until a null output is obtained. The digital device used for adjusting the reference voltage is then decoded and read out as the digital equivalent of the analog signal. This type of conversion of a signal from either voltage or charge to equivalent digital bit weights typically poses two major problems. First, it is often difficult to establish an exacting ratio between each successive bits. The conventional solution has been to trim the bit weights either mechanically or electronically, which has not achieved the accuracy desired in high precision ADC processes.
Second, power dissipation is always a major concern in conversion systems using amplifiers, comparators, and resistor ladders. Heat generated in the conversion processes by those components may be transferred to the detectors, which are usually placed adjacent to the signal processing circuitry.
Therefore, it is an object of the present invention to convert a charge packet representative of a signal into digital bit weights for further signal processing in a simplified manner.
It is also an object of the present invention to obviate the need to establish an exacting ratio between each successive bits in the conversion process.
It is another object of the present invention to reduce power dissipation generated by the conversion process.